AROUND 80 per cent of Australian grain farmers will be using some form of harvest weed seed control (HWSC) by the end of next year according to research from Weed Smart.

This will mark a 40pc jump since 2014, when around 40pc of growers had some of HWSC strategy.

The control methods used still vary markedly, with Weed Smart saying there are six main HWSC strategies, with farmers making their choices based on set-up cost, the amount of nutrients the method takes out of the soil and labour requirements.

There is widespread agreement that the ultimate HWSC tool would complete the weed seed control in one pass at harvest, retain all stubble and nutrients and not require any follow-up work such as marketing hay or burning chaff.

At present there are two units that meet those specifications, the iHSD (Integrated Harrington Seed Destructor) and the Seed Terminator.

Both chaff impact mill machines render the weed seed unviable, causing the destruction of over 95 per cent of the weed seed that enters the mills.

With the machines in relative commercial infancy there have been the usual teething problems, however the overall value was undeniable.

Kondinin Group Manager of Research and Development, Ben White interviewed 20 growers using either the iHSD or Seed Terminator during the 2017 harvest and reported that their observations suggested both brands were achieving over 95 per cent reduction in seed viability.

He said improvements needed to be made in handling high levels of chaff and operating in green or weedy crops, where the green matter chokes up the machine.

“Both types of impact mills ran into the same real-world problems of handling high flow rates of chaff, choking on green crop or weed matter and significant damage to the mills from any sand or soil that is picked up by the harvester,” he said.

The other major downfall, according to Mr White, was the reduction in header capacity.

“Both machines also caused a reduction in harvester capacity of between 12 and 20 per cent in wheat, even though the harvesters had been remapped.

“This is a significant cost that growers must allow for through machine depreciation and base hourly operating costs, as more hours are needed to harvest the same area of crop.”

Mr White also noted the machines generated significantly more dust, due to the chaff being completely smashed up.

In turn, he said this meant growers needed to blow down their headers more often to reduce fire risk.

However, he was optimistic of the machines’ long term success.

“Although the problems outlined here are important, they are all likely to be resolved as this technology matures in the commercial world.”

In terms of costs, benchmarking by the Australian Herbicide Resistance Initiative (AHRI) found chaff impact mills cost $16-17 a hectare compared to $22/ha for narrow windrow burning and $6-7/ha for chaff tramlining and chaff lining, depending on crop yield and area.

In addition to the weed control benefits achieved through the use of any HWSC method, the chaff impact mill option also reduces crop volunteers.